Fluid motor dumping system, including a cylinder head valve



1956 A. c. KELLE 2,730,588

FLUID MOTOR DUMPING SYSTEM, INCLUDING A CYLINDER HEAD VALVE Filed D80.19, 1952 2 Sheets-Sheet l SOURCE OF GAS UNDER PRESSURE 1956 A. c KELLE,730,588

FLUID MOTOR DUMPING SYSTEM, INCLUDING A CYLINDER HEAD VALVE Filed Dec.19, 1952 2 Sheefcs-Sheet 2 SOURCE OF 62 GAS UNDER PRESSURE 2) Wu mamaQMMW- United States PatentO FLUID MOTOR DUMPING SYSTEM, INCLUDING ACYLINDER HEAD VALVE Arthur C. Kelle, Stoughton, Mass., assignor to AllisChalmers Manufacturing Company, Milwaukee, Wis.

Application December 19, 1952, Serial No. 326,831

7 Claims. (Cl. 200-82) This invention relates to circuit breakers andmore particularly, to pneumatically operated high speed circuitbreakers.

One of the problems existing in the prior art which limited the speed ofoperation of a pneumatically operated circuit breaker was the excessivetime needed to reclose the circuit breaker contacts. Part of the timedelay in closing the contact of the circuit breaker was due to the slowacting air dumping means used to exhaust the air under pressure in thecylinder of the contact actuating fluid motor.

In order to reduce the time needed to reclose the arcing contacts, a newand improved fluid operated mechanism is provided comprising amechanical trip free mechanism for opening and closing a pair of arcingcontacts, a fluid motor having a dumping valve responsive to adiiference in pressure and having a dumping area which extends alongsubstantially the entire periphery of the head of the fluid motor foroperating the trip free mechanism, and a pilot dumping valve responsiveto the position of any movable element indicative of the relativecompleteness of the closing operation of the trip free mechanism.

It is therefore one object of the present invention to provide a new andimproved pneumatic circuit breaker operating system capable of effectinghigh speed opening and reclosing of the circuit breaker.

Another object of this invention is to provide a new and improvedpneumatic circuit breaker operating mechanism of the cylinder and pistontype in which the exhaust gases are dumped in a manner which permitsrapid piston reversal action.

A further object of this invention is to provide a new and improvedpneumatically operated trip free operating mechanism for a circuitbreaker in which the dumping action of the operating mechanism occurs inresponse to the position of any movable element indicative of therelative completeness of the closing operation of the trip freemechanism.

Other objects and advantages of the invention will become apparent fromthe following description when read in connection with the accompanyingdrawings, in which:

Fig. 1 is a view, partly in section, of a circuit breaker operatingsystem in contact closed position embodying the present invention; and

Fig. 2 is a side elevation partly in section on an enlarged scale of thecircuit breaker operating mechanism illustrated in Fig. 1 in contactopen position.

Referring more particularly to the drawings by characters of reference,Figs. 1 and 2 illustrate a pneumatically operating trip free mechanism11 for a circuit breaker 12. The pneumatically operating trip freemechanism 11 comprises a pneumatic motor 13 of the cylinder and pistontype and a trip free type linkage 14. Motor 13 and circuit breaker 12are operatively connected by linkage 14.

As diagrammatically shown, the circuit breaker 12 comprises a pair ofstationary contact members 15 and a movable contact member 16. Thecircuit breaker 12 is biased to open circuit position by means ofaccelerating spring 17. The movable contact member 16 is supported by abreaker rod 18 which, in turn, is supported by lever 19 pivoted at 20.Lever 19 is connected to the trip free operating linkage 14 by means ofoperating rod 21.

The operating linkage 14 comprises a lever22 pivoted at 23 and a lever24 pivoted at 25. Levers 22 and 24 are interconnected by a togglecomprising two toggle elements 26 and 2'7. Toggle element 26 ispivotally connected to lever 24 by a pin carrying a roller 28, andtoggle element 27 is pivotally connected at 23 to lever 22. Toggleelements 26 and 27 are pivotally joined together by a pin 30. Pin 30supports a roller 31 which is acted upon by an operating ram 32.

The contact closed position of the operating linkage 14 is illustratedin Fig. 1 and the contact open position of the operating linkage isillustrated in Fig. 2. In the contact closed position of the operatinglinkage 14, the upper position of pin 30 and roller 31 is controlled byan abutment 36. This abutment is made of any suitable resilient materialand is adapted to minimize vibrations of the frame of the trip freemechanism 11 due to the impact of linkage 14 upon abutment 36. In theclosed position of the circuit breaker 12, pin 30 forming the joint orconnection between toggle elements 26 and 27 is supported by a springbiased prop 33 as shown in Fig. 2. Spring 34 resets linkage 14 upon atrip free operation. Spring 34 is secured at one end on the frame of thetrip free operating mechanism 11 and at the other end to a lug 35 oftoggle element 27.

The circuit breaker 12 is tripped by spring 17 upon a predeterminedmovement of a tripping mechanism 40. Tripping mechanism 40 comprises afirst lever 41 pivoted at 42, a second lever 43 pivoted at 44, and atrip solenoid 45 comprising a plunger 46 adapted to act on lever 43.Plunger 46 can be operated either electromagnetically by energizingsolenoid 45 or mechanically by manual means, i. e., by operation of alever 47 pivoted at 48. Upon rotation of lever 43 about point 44 in thecounterclockwise direction, lever 41 is free to pivot about pin 42 inthe counterclockwise direction under the action of a force componenttransmitted to it by roller 28. The rotation counterclockwise of lever41 causes counterclockwise movement of lever 24 followed by collapse ofthe toggle formed by toggle elements 26 and 27 and return of lever 24 tothe position shown to cause the separation of the circuit breakercontacts 15, 16. Fig. 2 illustrates the linkage mechanism 14 in thetoggle broken position with lever 41 reset to the latching position.

In order to close the circuit breaker'12, compressed gas is admitted tofluid motor 13 through a pipe 50, solenoid valve 51, pipe 52, and aventing means or dump valve 53 comprising castings 54 and 55. Motor 13comprises a cylinder 57 and a piston 58 which is biased downwardly by aspring 59 resting against the top of cylinder head 49 of cylinder 57.Piston 58 is provided with a stepped abutment surface 80. The cylinderhead 49 is mounted in the downstream end of cylinder 57 and is providedwith abutment surfaces 82 and 83 adapted to cooperate with abutmentsurfaces 80, 81 on piston 58. A felt cushion 34 is arranged betweencylinder head 49 and a top plate for receiving the shock transmitted tocylinder head 49 upon impact thereon of piston 58. Piston 53 isconnected to ram 32 which coacts with roller 31 of linkage mechanism 14toclose the circuit breaker contacts 15, 16.

Casting 54 defines two passages, an intake passage 60 and an exhaustpassage 61. Casting 55 defines a discharge ring providing a plurality ofexhaust passages 62 separated by spacers 63. Bolts 64 passing throughspacers 63 tie cylinder 57 to castings 54 and 55.

Castings 54, 55 provide the housing for dump valve 53. Dump valve 53further comprises a plate or element 67 biased by a spring 63 in theupward direction against valve seats 69 and 7t defined by casting 55.Plate 67 is provided with perforations 71 adapted to be closed by asecond nonperforated plate 72 arranged on the downstream side of plate67, which faces piston 58. Plate 72 is biased by springs 73 againstplate 67 and permits gas under pressure to flow upward only throughperforation 71. The travel of plate 72 in upward direction is limited byabutments 7 4.

As shown in Fig. l, dumping of gas under pressure previously admittedthrough passage 66 to cylinder 57 may be effected by a piston type pilotvalve 88. Valve 88 comprises a cylindrical valve body 89, a valveelement 9% movably arranged within valve body 89 and biased to closedposition by means of a helical spring 91. Valve element 99 is in theshape of a piston with one end of spring 91 resting against the innerside of element 90 and the other end of spring 91 resting upon the baseof the valve body 89. Valve body 89 is provided with an intake opening92 and an exhaust opening 93. Pipe 94 interconnects exhaust passage 61of the dump valve 53 with intake opening 92 of valve 88. The top ofvalve body 89 is provided with a screw threaded opening 93. Cylinder '7of motor 13 is provided with an orifice 95 which is uncovered toward theend of each closing stroke of piston 58 so as to permit passage ofcompressed gas previously admitted to motor 13 through passage 60 todump valve 88. A permanently open duct 96 interconnects orifice 95 withopening 98.

The circuit breaker system in Fig. l of the drawings is shown with thecontacts 15 and 16 in the closed circuit position and the trippingmechanism in the corresponding position. Upon the energization of tripsolenoid 45, plunger 46 actuates lever 43 counterclockwise about point44. After a predetermined movement of lever 43, lever 4-1 is released torotate counterclockwise about point 42 under the action of a forcecomponent transmitted to it from roller 28. The counterclockwiserotation of lever 41 releases or unlocks the tripping mechanism 14. Uponcounterclockwise movement of lever 41, roller 28 moves upward under theaction of spring 17 causing the collapse of the toggle formed byelements 26 and 27 and the separation of contacts 15, 16. During thecollapse of elements 26, 27, pin 3!) slides on prop 33.

Upon the complete collapse of the toggle formed by elements 26, 27,roller 28 settles back on its support 37, and lever 41 rotates clockwiseunder its biasing means to its original position where it holds roller28 against its support 37. Trip latch 43 rotates back to its originalposition by the action of a spring biasing means (not shown) to holdlever 41 in its original position. The circuit breaker trip mechanism isthen in the position illustrated in Fig. 2.

To close the circuit breaker contacts 15 and 16 and to return the tripfree linkage 14 to the position shown in Fig. l, solenoid valve 51 isenergized to permit gas under pressure to flow from a reservoir (notshown) through pipe 50, solenoid valve 51, pipe 52, passage 60 into achamber 97 formed by castings 54, 55 on the upstream end of plate 67.When the pressure in chamber 97 reaches a predetermined value, plate 72is lifted from plate 67 against the bias of springs 73. The movement ofplate 72 upward opens ports 71 to permit compressed air to entercylinder 57 and to move piston 53 and ram 32 upward. The closing forceof motor 13 is applied to linkage 14 by engagement of ram 32 and roller31. Toggle elements 26 and 27 in moving upward during a closing strokeof piston 58, rotate lever 22 about its pivot point 23 in the clockwisedirection. That rotary motion of lever 22 causes operating rod 21 tomove downward. The downward movement of rod 21 causes lever 19 to rotatecounterclockwise about its pin 2%, thereby closing the breaker 12against the action of accelerating spring 17.

When the toggle elements 26 and 27 reach prop 33 in their upwardmovement under the action of piston 58 and ram 32, pin 30 biases prop 33clockwise and slides on it until roller 31 reaches abutment 36. Afterpin 30 slides on prop 33, prop 33 rotates counterclockwise under theaction of its biasing means 38 until it is in a position to support pin30. Lever 41 and trip latch 43 retain roller 28 in position adjacentstop 37. The toggle formed by elements 26 and 27 is retained in contactclosed position by the combined action of prop 33, lever 41 and latch43.

A closing operation is completed when prop 33, lever 41, and latch 43have closed the contacts and locked the toggle elements in contactclosed position. Then the supply of compressed gas may automatically beshut off. This may be achieved, for instance, by a limit switch (notshown) controlled by pin 25. Assume that the circuit breaker was closedon an overload, so that upon closure of its contacts 15, 16, solenoid 4Swithdraws latch 43 and does not restrain the breaker in closed circuitposition. he breaker then reopens under the action of acceleratingspring 17. However, the downward resetting movement of the ram isrelatively slow on account of the decelerating action, or dashpotaction, of fluid motor 13. Even if the supply of compressed gas is shutoiT from motor 13 and the lower side of motor 13 is being vented toatmosphere by prior art venting means, the decelerating effect of motor13 might be too large to permit an instantaneous reclosing of thecircuit controlled by the breaker. The dumping valve 53 shown incastings 54, 55 and dumping valve 88 are, however, so effective as topreclude any delay in the reclosure of the breaker.

Dumping of gas under pressure through inlet passage 69 to chamber 97 andcylinder 57 may be effected by piston type valve 88 and dumping valve53, When piston 58 of motor 13 uncovers orifice 95 toward the end of itscircuit breaker closing stroke, compressed gas from cylinder 57 flowsthrough orifice 95, duct 96 into valve body 89 to depress valve element99 against the bias of spring 91. This movement of valve element 90effects initial opening of valve 88, permitting compressed gas fromchamber 97 to enter through intake opening 92 into the body 89 of valve88, tending to push valve element 90 farther down to uncover exhaustport or opening 93. Upon uncovering of opening 93, gas under pressurebelow plates 67 and 72 is free to flow through exhaust passage 61,intake opening 92, the space within valve 38 above valve element 90 andexhaust opening 93 to atmosphere. When valve 88 has been wide opened bycompressed gas admitted to it through passage 61, a high pressure zoneforms on top of valve element 90, tending to maintain valve element 90in its open position against the bias of spring 91. Thus, valve element90 remains safely in its open position when, as a consequence of thereversal of the movement of piston 58 under the action of spring 59,orifice 95 in cylinder 57 is reclosed or obstructed by piston 53 as itmoves in the downward direction. In the position of valve 88 shown inFigs. l and 2, valve element 90 shuts off intake opening 92 from theinside of valve body 89 and, as long as this is the case, valve 88cannot be opened by any pressure of gas in passage 61.

Upon the opening of dump valve 88, the gas under pressure in chamber 97is exhausted to atmosphere and plates 67 and 72 are forced downward bythe pressure in cylinder 57 of motor 13. The downward movement of plates67 and 72 open exhaust passages 62 which exhaust substantially all ofthe gas under pressure inside of cylinder 57 and'downstream of piston 58to atmosphere. The area of passages 62 available for dumping air fromthe inside of cylinder 57 is equal to the entire periphery of thecylinder end extending over 360 degrees, minus the relatively small areaoccupied by spacers 63. The high dumping eifectiveness of this circuitbreaker system is predicated upon the fact that almost 360 degrees ofthe periphery of the cylinder head formed by castings 54, 55 have beenmade available for the purpose of gas dumping.

Cracking of valve 88 by compressed gas supplied through duct 96 tothetop of valve element 90 occurs close to the end ofeach closing stroke ofpiston 58. There must be sufficient power behind piston 58 to insure themovement of the latch mechanism 14 to the position at which prop 33 andlatch 41 pin the toggle elements in contact closed position beforecompressed gas can be dumped from fluid motor 13. The moment the breaker12 is restrained in closed circuit position, any gas under pressurewithin the cylinder 57 of motor 13 is instantly completely dumped. Ifthe latch mechanism 14 performs properly upon closing of circuit breaker12 by fluid operated motor 13, the circuit breaker remains in closedcircuit position (unless it should be tripped at that time eithermanually or automatically). Dumping of gas under pressure throughpassages 61 and 62 will nevertheless occur and result in high speedreversal of the movement of piston 58 to its position in Figs. 1 and 2.Piston 58, upon having reached that position, is ready to performanother closing operation.

Initial opening of dumping valves 53 and 88 occurs irespective of thecondition of the circuit controlled by the breaker, and dumping does notdepend upon the proper operation of any electroresponsive trip device.Where the operation of a valve for dumping of compressed gas from thecylinder of a fluid operated circuit breaker operating motor is madedependent upon the operation of an electroresponsive trip device, thedump valve does not afford any protection against the harmfulconsequences of a latch failure. Such an operating mechanism for circuitbreakers would call for the provision of additional means for guardingagainst the harmful consequences of a latch failure, e. g., anadditional dump valve which opens automatically when the supply ofcompressed gas is shut off from the breaker operating motor.

Mechanism 14 is trip free in that, if latch 41 is with drawn whilepiston 58 is closing contact 16, lever 24 rotates counterclockwise andthereby prevents the transmission of closing effort from ram 32 toroller 31. Lever 22 therefore remains in the position shown in Fig. 2 orreturns to that position if it has been moved toward or into theposition shown in Fig. 1 and the circuit breaker cannot close.

Although but one embodiment of the present invention has beenillustrated and described, it will be apparent to those skilled in the,art that various changes and modifications may be made therein withoutdeparting from the spirit of the invention or from the scope of theappended claims.

it is claimed and desired to secure by Letters Patent:

'1. In an operating mechanism for circuit breakers, a motor operable bygas under pressure and comprising a cylinder and a piston movablyarranged therein, a source of gas under pressure, means for admittinggas under pressure from said source to one end of said cylinder to closethe breaker, spring means for returning said piston to the initialposition thereof upon closing of the breaker, a collapsible linkage ofthe trip free type for operatively relating the breaker to said motor,tripping means for causing collapse of said linkage to cause opening ofthe breaker, a ram on said piston separate from said linkage andcooperating therewith upon collapse thereof for reclosing the breaker,means for venting said cylinder to cause said spring means to rapidlyreturn said piston to said initial position thereof, said venting meanscomprising a valve element arranged in said end of said cylinder,resilient means for biasing said element to closed position to closesaid end of said cylinder, pilot means for cracking said venting means,said pilot means including a piston type valve, resilient means forbiasing said piston type valve to closed position, means defining apassage from the upstream side of said element to atmosphere forming anintegral part of said pilot means for reducing the fluid pressure on theupstream side of said element and for holding said pilot valve in anopen position by the action of gas under pressure being vented throughsaid passage, and means for cracking said pilot valve to open said vent-7 V 6 ing means to exhaust the fluid in said cylinder to atmospherecomprising means defining an orifice in said cylinder controlled by saidpiston and means defining a permanently open duct for connecting saidorifice to said pilot valve.

2. In an operating mechanism for circuit breakers, a motor operable bygas under pressure and comprising a cylinder and a piston movablyarranged therein, a source of gas under pressure, means for admittinggas under pressure from said source to one end of said cylinder to closethe breaker, spring means for returning said piston to the initialposition thereof upon closing of the breaker, a collapsible linkage ofthe trip free type for operatively relating the breaker to said motor,tripping means for causing collapse of said linkage to cause opening ofthe breaker, a ram on said piston separate from said linkage andcooperating therewith upon collapse thereof for reclosing the breaker,means for venting said cylinder to cause said spring means to rapidlyreturn said piston to said initial position thereof, said venting meanscomprising a valve element arranged at said end of said cylinder,resilient means for biasing said element to closed position to closesaid end of said cylinder, means defining a one way passage through saidelement for fluid to flow to the downstream side of said element forproviding fluid under pressure to actuate said piston, pilot means forcracking said venting means, said pilot means including a piston typevalve, resilient means for biasing said piston type valve to closedposition, means defining a passage from the upstream side of saidelement to atmosphere forming an integral part of said pilot means forreducing the fluid pressure on the upstream side of said element and forholding said pilot valve in open position by the action of gas underpressure being vented through said passage, and means for cracking saidpilot valve to open said venting means to exhaust the fluid in saidcylinder to atmosphere comprising means defining an orifice in saidcylinder controlled by said piston and means defining a permanently openduct for connecting said orifice to said pilot valve.

3. In an operating mechanism for circuit breakers, a motor operable bygas under pressure and comprising a cylinder and a piston movablyarranged therein, a source of gas under pressure, means for admittinggas under pressure from said source to one end of said cylinder to closethe breaker, spring means for returning said piston to the initialposition thereof upon closing of the breaker, a collapsible linkage ofthe trip free type for operatively relating the breaker to said motor,tripping means for causing collapse of said linkage to cause opening ofthe breaker, a ram on said piston separate from said linkage andcooperating therewith upon collapse thereof for reclosing the breaker,means for venting said cylinder to cause said spring means to rapidlyreturn said piston to said initial position thereof, said venting meanscomprising a valve element arranged at said end of said cylinder,resilient means for biasing said element to a closed position to closesaid end of said cylinder, means defining a passage to atmospherecontrolled by said element for exhausting the said gas from said end ofsaid cylinder, and means for reducing the pressure on one side of saidelement to actuate said element to valve open position, said elementupon actuation to valve open position opening said passage definingmeans, pilot means for cracking said venting means, said pilot meansincluding a piston type valve, resilient means for biasing said pistontype valve to a closed position, means defining a second passage fromthe upstream side of said element to atmosphere forming an integral partof said pilot means for reducing the fluid pressure on the upstream sideof said element and for holding said pilot valve in an open position bythe action of gas under pressure being vented through said secondpassage, and means for cracking said pilot valve to open said ventingmeans to exhaust the fluid in said cylinder to atmosphere comprisingmeans defining an orifice in said cylinder controlled by said piston andmeans defining a permanently open duct for connecting said orifice tosaid pilot valve.

4. In an operating mechanism for circuit breakers, a motor operable bygas under pressure and comprising a cylinder and a piston movablyarranged therein, a source of gas under pressure, means for admittinggas under pressure from said source to one end of said cylinder to closethe breaker, spring means for return said piston to the initial positionthereof upon cios 1g of the breaker, a collapsible linkage of the triptree type for operatively relating the breaker to said motor, trippingmeans for causing collapse of said linkage to cause opening of thebreaker, a ram on said piston separate from said linkage and cooperatingtherewith upon collapse thereof for reclosing the breaker, means forventing said cylinder to cause said spring means to rapidly return saidpiston to said initial position thereof, said venting means comprising avalve element arranged at said end of said cylinder, resilient means forbiasing said element to close said end of said cylinder, means defininga passage to atmosphere comprising an area extending over substantiallythe entire periphery of said cylinder, said passage defining meanscontrolled by said element provided for exhausting to atmosphere the gasfrom said end of said cylinder, and means for reducing the pressure onone side of said element to actuate said element to valve open positionto exhaust gas under pressure from the upstream side of said pistonthrough said passage to atmosphere, pilot means for cracking saidventing means, said pilot means including a piston type valve, resilientmeans for biasing said piston type valve to closed position, meansdefining a second passage from the upstream side of said element toatmosphere forming an integral part of said element for reducing thefluid pressure on the upstream side of said element and for holding saidpilot valve in an open position by the action of gas under pressurebeing vented through said second passage, and means for cracking saidpilot valve to open said venting means to exhaust the fluid in saidcylinder to atmosphere comprising means defining an orifice in saidcylinder controlled by said piston and means defining a permanently openduct for connecting said orifice to said pilot valve.

5. In an operating mechanism for circuit breakers, a motor operable bygas under pressure and comprising a cylinder and a piston movablyarranged therein, a source of gas under pressure, means for admittinggas under pressure from said source to said cylinder to close thebreaker, spring means for returning said piston to the initial positionthereof upon closing of the breaker, a collapsible linkage of the tripfree type for operatively relating the breaker to said motor, trippingmeans for causing collapse of said linkage to cause opening of thebreaker, a ram on said piston separate from said linkage and cooperatingtherewith upon collapse thereof for reclosing the breaker, means forventing said cylinder to cause said spring means to rapidly return saidpiston to said initial position thereof, said venting means comprising adififerential valve element arranged at said end of said cylinder,resilient means for biasing said element to close said end of saidcylinder, means defining a discharge ring surrounding said element forproviding a plurality of passages to atmosphere, means for reducing thepressure on one side of said element to actuate said element to openposition to exhaust gas under pressure from said end of said pistonthrough said passages to atmosphere, and pilot means for cracking saidventing means, said pilot means including a piston type valve, resilientmeans for biasing said piston type valve to closed position, meansdefining a passage from the upstream side of said element to atmosphereforming an integral part of said element for reducing the fluid pressureon the upstream side of said element and for holding said pilot valve inopen position by the action of gas under pressure being vented throughsaid passage, means for cracking said pilot valve to open said ventingmeans to exhaust the fluid in said cylinder to atmosphere comprisingmeans defining an orifice in said cylinder controlled by said piston andmeans defining a permanently open duct for connecting said orifice tosaid pilot valve.

6. In an operating mechanism for circuit breakers, a motor operable bygas under pressure and comprising a cylinder and a piston movablyarranged therein, a source of gas under pressure, means for admittinggas under pressure from. said source to one end of said cylinder toclose the breaker, spring means for returning said piston to the initialposition thereof upon closing of the breaker, a collapsible linkage ofthe trip free type for operatively relating the breaker to said motor,tripping means for causing collapse of said linkage to cause opening ofthe breaker, a ram on said piston separate from said linkage andcooperating therewith upon collapse thereof for reclosing the breaker,means for venting said cylinder to atmosphere to cause said spring meansto rapidly return said piston to said initial position, said ventingmeans comprising a valve element arranged at said end of said cylinder,resilient means for biasing said element to close said end of saidcylinder, means defining a passage to atmosphere comprising an areaextending over the entire periphery of said cylinder, said passagedefining means controlled by said element, and means for reducing thepressure on the upstream side of said element to actuate said element tovalve open position to exhaust gas under pressure from said cylinderthrough said passage to atmosphere, said pressure reducing meanscomprising a piston type valve, resilient means for biasing said pistontype valve to closed position, means defining a passage from theupstream side of said element to atmosphere forming an integral part ofsaid pressure reducing means for reducing the fluid pressure on theupstream side of said element, and means for cracking said pressurereducing means to open said venting means to exhaust the fluid in saidcylinder to atmosphere.

7. in an operating mechanism for circuit breakers, a motor operable bygas under pressure and comprising a cylinder and a piston movablyarranged therein, a source of gas under pressure, means for admittinggas under pressure from said source to one end of said cylinder to closethe breaker, spring means for returning said piston to the initialposition thereof upon closing of the breaker, a collapsible linkage ofthe trip free type for operatively relating the breaker to said motor,tripping means for causing collapse of said linkage to cause opening ofthe breaker, a ram on said piston separate from said linkage andcooperating therewith upon collapse thereof for reclosing the breaker,means for venting said cylinder to atmosphere to cause said spring meansto rapidly return said piston to said initial position, said ventingmeans comprising a valve element arranged at said end of said cylinder,resilient means for biasing said element to close said end of saidcylinder, means do fining a discharge ring surroundin said element forproviding a plurality of passages to atmosphere, means for reducing thepressure on the upstream side of said element to actuate said element tovalve open position to exhaust gas under pressure from said cylinderthrough said passages to atmosphere, said pressure reducing meanscomprising a piston type valve, resilient means for biasing said pistontype valve to closed position, means defining a passage from theupstream side of said element to atmosphere forming an integral part ofsaid pressure reducing means for reducing the fluid pressure on theupstream side of said element and for holding said pilot valve in anopen position by the action of gas under pressure being vented throughsaid passage, and means 9 for cracking said pilot valve to open saidventing means References Cited in the file of this patent to exhaust thefluid in said cylinder to atmosphere com- UNITED STATES PATENTS prisingmeans defining an orifice in said cylinder controlled by said piston andmeans defining a permanently 1,953,789 Thumim 1934 open duct forconnecting said orifice to said pilot valve. 5 2,248,851 Canfield July1941 2,548,221 K6116 Apr. 10, 1951 2,578,204 Peek Dec. 11, 1951

